Questions on Stack Overflow are expected to relate to programming within the scope defined by the community. Consider editing the question or leaving comments for improvement if you believe the question can be reworded to fit within the scope. Read more about reopening questions here.
If this question can be reworded to fit the rules in the help center, please edit the question.

3 Answers
3

We are dealing with a bit of abuse of terminology. Originally "bandwidth" means the width of the band that you have available to transmit (or receive) on. The term has been co-opted to also mean the amount of digital data you can transmit (or receive) on a line per unit time.

Here's an example of the original meaning. FM radio stations are spaced 200 kHz apart. You can have a station on 95.1 MHz and another one on 94.9 MHz and another one on 95.3 MHz, but none in between. The bandwidth available to any given FM radio station is 200 kHz (actually it may be less than that if there is a built-in buffer zone of no-mans-land frequencies between stations, I don't know).

The bandwidth rating of something like a coaxial cable is the range of frequencies of the electromagnetic waves that it is designed to transmit reliably. Outside that range the physical properties of the cable cause it to not reliably transmit signals.

With (digital) computers, bandwidth almost always has the alternate meaning of data capacity per unit time. It's related though, because obviously if you have more available analog band width, it lets you use a technology that transmits more (digital) data at the same time over that carrier.

That's the bandwidth of the signal that can be sent through the cable. You might want to have a read of Nyquist-Shannon sampling theorem to read about how that relates to the data that can be transmitted.

How the "MHz relate to Kb" depends on the method for transmitting the data, which is why you'll see cables rated with a bandwidth in MHz like you've seen.

Coaxial cable is not a "network" but a transmission medium. For physical reasons the bandwidth must be measured in Hz, consider in fact that we're talking here of electromagnetic signals and not bits.
When you move to the "network" side, in particular digital networks, the capacity is measured in bps. Note that while a bandwidth (MHz) increase will lead generally to a bps increase, the final bps depends on many factors which depend for example on the digital modulation scheme (at low level) and the network protocol (at higher level). A typical case is the "symbol" representation, which gives you the information of how many bits are sent on a single "pulse".
But the subject is really huge and cannot be faced in a single answer here, I recommend you to read a good book on electric communications to have a clear picture on the subject.